This invention relates to rotary encoders for optically detecting a rotational position of an object.
The encoders of the type referred to are arranged such that a detection shaft is journalled rotatably within a casing, and a pair of light emitting and receiving means are opposed to each other in the casing. The light receiving means receives a light beam from the light emitting means through slits made in a stationary slit plate positioned between the light emitting and receiving means and also in a rotary slit wheel mounted on the detection shaft. Such encoders are utilized for detecting the rotational angle of the detection shaft interlocked with a rotating object to be detected in a measuring or control mechanism.